Delphi DLL

Firebase GET - Reading Data

See more Firebase Examples

Demonstrates how to read parts of a Firebase JSON database. The data used in this example is at Chilkat Firebase Pigs Database, and is shown here:

Delphi DLL

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, FileAccess, Rest, AuthGoogle, StringBuilder, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
fac: HCkFileAccess;
accessToken: PWideChar;
rest: HCkRest;
authGoogle: HCkAuthGoogle;
jsonResponse: PWideChar;
piggyPath: HCkStringBuilder;
shallow: HCkJsonObject;
piggyData: HCkJsonObject;
count: Integer;
i: Integer;
piggyJson: PWideChar;

begin
success := False;

// Demonstrates how to read parts of a Firebase JSON database.

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// This example assumes a JWT authentication token, if required, has been previously obtained.
// See Get Firebase Access Token from JSON Service Account Private Key for sample code.

// Load the previously obtained Firebase access token into a string.
fac := CkFileAccess_Create();
accessToken := CkFileAccess__readEntireTextFile(fac,'qa_data/tokens/firebaseToken.txt','utf-8');
if (CkFileAccess_getLastMethodSuccess(fac) <> True) then
  begin
    Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
    Exit;
  end;

rest := CkRest_Create();

// Make the initial connection (without sending a request yet).
// Once connected, any number of requests may be sent.  It is not necessary to explicitly
// call Connect before each request.  
success := CkRest_Connect(rest,'chilkat.firebaseio.com',443,True,True);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;
// If authentication is required...
authGoogle := CkAuthGoogle_Create();
CkAuthGoogle_putAccessToken(authGoogle,accessToken);
CkRest_SetAuthGoogle(rest,authGoogle);

// Chilkat's sample data (pig-rescue data) is publicly readable at: https://chilkat.firebaseio.com/.json

// Let's get the animals with the shallow parameter so we can see how many pigs exist.
jsonResponse := CkRest__fullRequestNoBody(rest,'GET','/pig-rescue/animal.json?shallow=true');
if (CkRest_getLastMethodSuccess(rest) <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// The JSON returned should look like this:  
// {"-KI3bD-FU_Dake7sYOiP":true,"-KI3bD-FU_Dake7sYOiT":true,"-KI3bD-FU_Dake7sYOiS":true,"-KI3bD-FU_Dake7sYOiU":true,"-KI3bD-FU_Dake7sYOiV":true,"-KI3bD-FU_Dake7sYOiR":true,"-KI3bD-FU_Dake7sYOiQ":true}
Memo1.Lines.Add(jsonResponse);

// Parse the response so we can iterate over each pig in the database..
piggyPath := CkStringBuilder_Create();
shallow := CkJsonObject_Create();
piggyData := CkJsonObject_Create();
CkJsonObject_Load(shallow,jsonResponse);
count := CkJsonObject_getSize(shallow);
i := 0;
while i < count do
  begin

    // Get each individual pig's data.
    CkStringBuilder_Clear(piggyPath);
    CkStringBuilder_Append(piggyPath,'/pig-rescue/animal/');
    CkStringBuilder_Append(piggyPath,CkJsonObject__nameAt(shallow,i));
    CkStringBuilder_Append(piggyPath,'/.json');

    piggyJson := CkRest__fullRequestNoBody(rest,'GET',CkStringBuilder__getAsString(piggyPath));
    if (CkRest_getLastMethodSuccess(rest) <> True) then
      begin
        Memo1.Lines.Add(CkRest__lastErrorText(rest));
        Exit;
      end;

    // Show this piggy's data...
    // An example of one pig's data is shown here:
    // {"birth":"February, 1998","from":"Middle Ave.","gender":"F","in-date":"January, 2000",
    //   "name":"Molly II","picture":{"caption":"Molly in the Pasture","description":"Black pig","file":"molly_th.jpg"},
    //   "species":"pot belly pig","type":"Cathy's Herd"}
    Memo1.Lines.Add('---- ' + IntToStr(i) + ' ----');
    Memo1.Lines.Add(piggyJson);

    // Let's get the pig's name, and the caption of the picture.
    CkJsonObject_Load(piggyData,piggyJson);
    Memo1.Lines.Add('name: ' + CkJsonObject__stringOf(piggyData,'name'));
    Memo1.Lines.Add('caption: ' + CkJsonObject__stringOf(piggyData,'picture.caption'));

    i := i + 1;
  end;

// Note: In many of the Chilkat examples, you may notice strange ways
// of doing something that should be simpler and shorter.  For example,
// building the piggyPath (above) could've been written differently,
// with some simple string concatenation.
// 
// The reason is that the Chilkat examples are written in a 
// proprietary "example code" scripting language,
// and then automatically generated to each of the different programming
// languages you see on example-code.com.  The code generation is
// limited in what it can do.  For example, string concatentation
// is not yet a feature of the "example code" scripting language (as of May 2016), 
// and therefore you won't see the use of a programming language's string
// concatentation operators in any example.  
// 

CkFileAccess_Dispose(fac);
CkRest_Dispose(rest);
CkAuthGoogle_Dispose(authGoogle);
CkStringBuilder_Dispose(piggyPath);
CkJsonObject_Dispose(shallow);
CkJsonObject_Dispose(piggyData);

end;